How to Read the Utility's Water Quality Report

Why this matters

Every community water system in the country publishes a report each year that tells you what is in the water before it reaches the meter: its hardness, its disinfectant, its pH, and what its lead sampling found. A plumber about to install a tankless heater, a water treatment tech about to quote a filter, and a pool tech chasing scale can all read the answer to their first question from that report in ten minutes, for free. The same report is also easy to over-read. It describes the system's water on average across a year, not the water at one kitchen tap, and the customer asking "is my water safe" deserves an answer that knows the difference.

What the report is and who has to publish it

The Consumer Confidence Report (CCR) is required under the Safe Drinking Water Act by EPA's rule at 40 CFR Part 141, Subpart O. It applies to community water systems: public systems serving at least 15 service connections or 25 year-round residents. That is your city or water district, and also a mobile home park or subdivision with its own wells. Most must deliver the report to customers by July 1 each year, covering the previous calendar year.

It does not apply to private wells, which nobody tests unless the owner does (see related: Private Wells and the Water Nobody Tests), or to non-community systems such as a school or workplace on its own well. States with primacy run the program and may add requirements.

A 2024 revision to the CCR rule added a second yearly delivery for larger systems and plain-language requirements, with compliance dates in 2027. Check your state drinking water program for what applies now.

Step 1: Get the right report

Find the system name and its public water system ID (PWSID) on the customer's water bill or the utility's website, then pull the most recent report from the utility or EPA's CCR search. In a house on a small private system, the property manager or HOA has it.

Why: neighboring towns, and sometimes different pressure zones of one utility, draw from different sources. What breaks if you skip it: you quote treatment for the city's river water to a house served by the district's wells.

Step 2: Read where the water comes from

The source section says surface water (river, lake, reservoir), groundwater (wells), or a blend, and whether the utility buys some water from another system. It also says how to get the source water assessment.

Why it matters to the trades: groundwater tends to be harder and steadier through the year; surface water tends to be softer but changes with the seasons, and a utility that blends sources can deliver noticeably different water in different months. What breaks if you skip it: you treat one test as the house's permanent water when the source changes seasonally.

Step 3: Read the detected contaminants table column by column

The core of the report is a table of regulated contaminants that were detected. The columns, roughly as most reports print them:

• MCLG, maximum contaminant level goal: the level below which no known health risk is expected. Not enforceable, and zero for some contaminants.
• MCL, maximum contaminant level: the enforceable limit. A treatment technique (TT) appears instead for contaminants regulated by required treatment.
• Level detected: the number compliance is judged on, which is not always a simple average. Disinfection byproducts, for example, are judged on the highest running annual average at any one sampling location.
• Range: the lowest and highest individual results. A level detected well under the MCL with a range that touches it means some samples ran high.
• Violation: yes or no. A violation section explains any yes, with the required health-effects language.
• Likely source: erosion of natural deposits, byproduct of disinfection, and so on.

What breaks if you skip it: you read the range's high number as the system's level, or the other way round.

Step 4: Read lead and copper differently from everything else

Lead and copper are regulated by a treatment technique with an action level, not an MCL, and they are sampled at customers' taps in homes most likely to have lead plumbing, not at the plant. The report gives:

• The 90th percentile result: 90 percent of sampled homes were at or below it.
• The number of sites above the action level.
• The action levels: 15 micrograms per liter (parts per billion) for lead and 1.3 mg/L for copper under the current rule. EPA's 2024 Lead and Copper Rule Improvements lower the lead action level to 10 micrograms per liter with compliance dates in 2027; the status of that rule has been revisited since, so check it with your state program.

A system whose 90th percentile is under the action level is in compliance even when some homes sampled above it. That is the line a customer needs explained: the report says the system's corrosion control is working, not that every house is fine. The report must also say how to find the utility's service line inventory, which records whether each service line is lead, galvanized requiring replacement, non-lead or unknown. See related: How to Check Whether a Service Line Is Lead.

What breaks if you skip it: you tell a customer in a 1940s house with a possible lead service line that "the report says lead is fine".

Step 5: Find the chemistry the trades actually use

Hardness, pH, alkalinity, total dissolved solids (TDS), sodium, chloride, iron and manganese are often in a separate table of unregulated or secondary characteristics, or on the utility's website rather than in the CCR. EPA's secondary standards (40 CFR 143.3) are non-enforceable federal guidelines for taste, odor, staining and scaling, though some states enforce them: pH 6.5 to 8.5, TDS 500 mg/L, chloride and sulfate 250 mg/L each, iron 0.3 mg/L, manganese 0.05 mg/L.

The other line to find is the disinfectant: free chlorine or chloramine (chlorine combined with ammonia, which lasts longer in the pipes). It matters more than its single line suggests:

• Ordinary activated carbon removes chlorine well and chloramine poorly; chloramine removal needs a filter rated for it.
• Chloramine must be removed for aquariums and for home dialysis.
• Chloramine is harder on some rubber parts than chlorine, which some plumbers see in flappers and seals.

What breaks if you skip it: you sell a whole-house carbon filter to remove "the chlorine taste" from chloraminated water, and the customer notices no difference.

Step 6: Say what the report cannot tell you

The report describes water at the system level, sampled at set points and summarized over a year. It does not show:

• The house's own plumbing: lead solder (banned in potable plumbing in 1986), older brass, galvanized pipe, or a water heater adding sediment.
• One tap on one day: a dead-end street with low water use can carry lower disinfectant and different chemistry than the system average.
• Anything after the meter: a softener, a filter, a well pump.
• Contaminants that were not detected or not required to be monitored that year. Federal limits for several PFAS were set in 2024, and EPA changed parts of that rule in 2025, so a given year's report may or may not include them; check the current status before you discuss them.

Where the question is about this house, the answer is a tap test by a certified laboratory, not the report. Health questions go to the utility, the state drinking water program or the local health department, not to the tech.

Worked through: a heater replacement and a filter question

A plumber is replacing a tank water heater with a tankless unit in a 1949 house, and the customer asks whether they need a filter "because of the lead". The utility's report, trimmed:

2026 WATER QUALITY REPORT (covers Jan-Dec 2025)
DETECTED REGULATED CONTAMINANTS
Item      Unit  MCLG  MCL  Level  Range    Viol
Nitrate   mg/L  10    10   2.1    0.4-2.1  No
TTHM      ug/L  n/a   80   41     18-62    No
Fluoride  mg/L  4     4    0.7    0.6-0.8  No
LEAD AND COPPER (2024 tap sampling, 30 homes)
Lead    ug/L  AL 15   90th pct 6    above AL 2
Copper  mg/L  AL 1.3  90th pct 0.4  above AL 0
OTHER CHARACTERISTICS (not regulated)
Hardness 180 mg/L   pH 7.8   Sodium 32 mg/L
Disinfectant: chloramine, avg residual 2.6 mg/L

What the plumber reads from it:

• Hardness. 180 mg/L divided by 17.1 is 10.5 gpg, the top of the "hard" band. That is a yearly figure, so some months may run higher. The tankless manual's hardness limit is the comparison; a field test on the day of install confirms it. See related: How to Check Water Hardness on a Service Call.
• Disinfectant. Chloramine. If the customer wants a filter for taste, it needs to be rated for chloramine.
• TTHM (total trihalomethanes, a disinfection byproduct). 41 against an MCL of 80, with a high single result of 62, so even the worst sample was under the limit. No violation.
• Lead. The 90th percentile, 6, is under the action level of 15, so the system complied. But 2 of 30 homes sampled above 15. The house was built in 1949, before the 1986 solder ban, and may have a lead or galvanized service line. The plumber checks the utility's service line inventory for the address and looks at the pipe where it enters the house before giving any opinion.

What the plumber tells the customer: the city's water meets its standards as a system; whether this house has a lead source is a question about this house's service line and plumbing, which the inventory and a certified lab test answer. If they want a point-of-use filter for drinking water in the meantime, it should be certified for lead reduction (NSF/ANSI 53, the standard certifying bodies test lead reduction against) and, for taste, for chloramine.

What would change the answer. If the report had shown a lead action level exceedance, the utility would be required to do public education and take further steps, and the customer's question gets a direct referral to the utility. If the inventory lists the service line as lead, that is the utility's replacement program and a plumber's quote for the private side, depending on how the local program splits ownership.

References

• EPA, Consumer Confidence Report Rule, 40 CFR Part 141 Subpart O
• EPA, Lead and Copper Rule and the 2024 Lead and Copper Rule Improvements (check current status)
• EPA, National Secondary Drinking Water Regulations, 40 CFR 143.3
• NSF/ANSI 53, drinking water treatment units for health effects, as used by product certifiers
• See related: How to Check Whether a Service Line Is Lead; Private Wells and the Water Nobody Tests